Inductive coil and method of making the same



Aug. 12, 1969 FEARQN ETAL 3,461,414

INDUCTIVE COIL AND METHOD OF MAKING THE .SAME

Filed May 13. 1968 5 Sheets-Sheet 1 36 40 Z I v 34A 55 Z/\/\/E/\/ 705 5 R. L. FEHE'UN Fe. I77. ETURLH Aug. 12, 1969 R, FEARON ETAL 3,461,414

INDUCTIVE COIL AND METHOD OF MAKING THE'SAME Filed May 13, 1968 3 Sheets-Sheet 2 Aug. 12, 1969 R FEARQN ET AL 3,461,414

INDUCTIVE COIL AND METHOD OF MAKING THE SAME Filed May 13, 1968 3 Sheets-Sheet 5 United States Patent 3,461,414 INDUCTIVE COIL AND METHOD 0 MAKING THE SAME Ralph L. Fearon, Raytown, and Robert M. Story, Lees Summit, Mo., assignors to Western Electric Company, glcorporated, New York, N.Y., a corporation of New ork Filed May 13, 1968, Ser. No. 728,650 Int. Cl. H011 15/10, 27/30 US. Cl. 336-192 Claims ABSTRACT OF THE DISCLOSURE Background of the invention One common way of forming an inductive coil for use in relays and the like is to wind a continuous length of fine insulated wire on a tubular core of a molded and flanged bobbin. One flange on the bobbin is generally provided with pro-formed metallic terminals for conductive attachment to the ends of the coil. Improved insulation between the ends of the coil and the main winding is accomplished by routing the coil ends into a suitable recess in the flange prior to terminal attachment. Such a recess, which is isolated from the main winding by an inner wall of the flange, is accessible to the core through one or more slots in the flange wall.

Rapid and inexpensive fabrication of coils with such an arrangement is hampered by the necessity of (1) molding terminal mounting slots in the bobbin flange in addition to the access slots and the recess and (2) inserting pre-formed metallic terminals in such mounting slots prior to winding.

Summary of the invention Such drawbacks may be eliminated with the technique of the present invention, wherein a bobbin flange is provided with an external reservoir for temporarily storing buffer lengths of the coil wire at the input and output ends of the main winding on the core. Such buffer lengths may be extended over the coil and soldered to heavy axial leads which pass through a plurality of radial slots in the flange to provide terminal access to the coil.

In an illustrative embodiment, the coil wire is initially wound around a peripheral surface of the flange several times, after which the wire is passed inwardly through one of the radial slots and wound around the bobbin core to form the coil. The wire is then passed outwardly through another of the radial slots, wound around the peripheral flange surface several more times, and terminated.

At this point the lengths of wire in the two sets of convolutions on the peripheral surface are unwound therefrom and passed inwardly through separate ones of the radial slots to extend in overlying relation with the wound coil on the core. A pair of leads are passed over the wound coil through separate ones of the radial slots, and the inner ends thereof are attached to the extended ends of the unwound convolutions to form the coil terminals.

Preferably, a first layer of insulating tape is placed over the coil before the unwound wire is passed thereover,

3,461,414 Patented Aug. 12, 1969 "ice and a second layer of tape is employed to secure the leads in place over the tape-wound coil.

Brief description of the drawing The nature of the invention and its advantages will appear more fully from the following detailed description taken in conjunction with the appended drawing, in which:

FIG. 1 is a side elevation, partly broken away, of a bobbin having a grooved flange constructed to provide a wire reservoir in accordance with the invention;

FIG. 2 is a side view, partially broken away, of the bobbin of FIG. 1 showing the detailed construction of the grooved flange;

FIGS. 3-6 are identical plan views of the bobbin of FIG. 2 during successive stages of coil winding thereon; and

FIG. 7 is a perspective view of a completed coil assembly wound on the bobbin of FIGS. l-6.

Detailed description Referring now to the drawing, FIG. 1 illustrates a coil bobbin 18 which may be molded from nylon or similar insulating material. The bobbin 18 includes an elongated cylindrical core 19 having an axis 21 and an outer peripheral surface 22 of radius A. The core 19 is bounded on longitudinally opposite ends by a conventional disc flange 23 and a composite grooved flange 24, respectively.

The flange 24 includes an inner disc 26 having a plurality of circumferentially space apertures 27a-27a (FIG. 2), illustratively slots, extending inwardly from a peripheral surface 28 of the inner disc 26. While four such slots are depicted in the illustrative embodiment, it will be apparent as the description proceeds that a greater or lesser number may be employed where appropriate.

The composite flange 24 further includes a central disc 29 axially abutting the inner disc 26. The central disc 29 has a pair of circumferentially spaced apertures 31a and and 31b, illustratively slots, extending inwardly from a peripheral surface 32. The slots 31a and 31b are disposed generally symmetrically with respect to the four slots 27 on the inner disc 26. The diameter of the peripheral surface 32 is smaller than the diameter of the peripheral surface 28.

The slots 27a and 27d on the inner disc 26 terminate, at their inner ends, at the diameter A of the core periphery 22 (FIG. 1). Similarly, the slots 31a and 31b (FIG. 2) in the central disc 29 terminate at their inner ends at the diameter A. In this way the slots 27a, 27d, 31a, and 31b provide access between the core periphery and the peripheral surface 32 of'the central disc 29. As shown, the remaining slots 27b and 27c in the inner disc 26 may be shallower than the slots 27 a and 27d.

The flange 24 also includes an outer disc 33 (FIG. 1) axially abutting the central disc 29. The outer disc 33, whose construction may be generally identical to that of the inner disc 26, includes a plurality of apertures 34a- 34d, illustratively slots (one of which, designated 34b, is shown in FIG. 1), individually corresponding to and aligned with the slots 27a27d in the inner disc 26. Each of the slots 34 extends inwardly from a peripheral surface 36 of the outer disc 33.

In addition, the outer disc 33 includes a boss 37 extending radially outward from a portion of the peripheral surface 36 that is diametrically opposite from the region of the slots 34a-34d.

The reduced-diameter central disc 29 defines, with an adjacent pair of walls 38 and 39 of the inner and outer discs 24 and 33, an annular reservoir 40 which is employed during the coil winding operation described below.

FIGS. 37 illustrate successive stages in the process of winding a coil about the bobbin 18 in accordance with the invention. As shown in FIG. 3, for example, an input end 41 of a continuous insulated wire 42 is initially anchored to the boss 37, as by winding several turns therearound. The wire is then routed from the boss 37 to the reservoir 40 in the direction of an arrow 43, and several auxiliary, or buffer, convolutions (represented by the numeral 44) of the wire are wound around the peripheral surface 32 of the central disc 29. The winding step maybe accomplished, e.g., by rotating the bobbin 18 about its axis 21 by suitable means not shown.

The wire 42 is then passed inwardly, as shown by an arrow 46, to the periphery of the bobbin core via the slot 31a in the central disc 29 and the slot 27a in the inner disc 26. The wire 42 is now convolutely wound on the bobbin core in a conventional manner to form a coil 47 on the core periphery 22. The number of turns on the coil 47 will depend, of course, on the contemplated application of the coil structure.

After the coil 47 is wound, the wire 42 is passed outwardly, as shown by an arrow 48 (FIG. 4), to the reservoir 40 through the slot 27d in the inner disc 26 and the slot 31b in the central disc 29. In addition, a layer 49 of insulating tape may be wrapped around the coil 47.

Within the reservoir 40, a second plurality of wire convolutions (represented by the numeral 50) are now wrapped around the peripheral surface 32 of the central disc 29 (e.g., by rotating the bobbin 18 about its axis 21 again). The wire is then routed back to the boss 37 in the direction of an arrow 51, and is anchored to the boss 37 by winding several additional turns therearound. After anchoring, the wire is severed.

Following the wire severing step, the anchored portions of the wire 42 on the boss 37 and the two sets of wire convolutions 44 and 50 on the peripheral surface 32 are unwound. One of the lengths of unwound wire, designated by the numeral 52 (FIG. extends outwardly from one end of the coil 47 through the radial slot 27a in the inner disc 26 to terminate at an inner coil end 53. The other length of unwound wire, designated by the numeral 54, extends outwardly from the other end of the coil 47 through the radial slot 27d in the inner disc 26 to terminate at an outer coil end 56. The unwound lengths of wire 52 and 54 are bent back on themselves as shown and extend inwardly via the intermediate radial slots 27b and 27c, respectively, to project over the tape-wrapped coil 47. Preferably, the wire lengths 52 and 54 are laid over the taped coil in such a manner that the coil ends 53 and 56 are in axial alignment with the respective slots 27a and 27d in the inner disc 26 and the corresponding slots 34a and 34d in the outer disc 33.

As shown in FIG. 6, a first elongated axial lead 58 of heavier gauge than the coil wire is laid in the aligned radial slots 34a and 27a in the outer and inner discs 33 and 26, respectively, to project over the taped coil 47 and terminate adjacent the inner coil end 53. In like manner a second axial lead 59 identical to the first lead 58 is laid in the aligned radial slots 34d and 27d to project over the wrapped coil 47 and terminate adjacent the outer coil end 56. The coil ends 53 and 56 are respectively soldered, as shown at 61 and 62, to the adjacent ends of the leads 58 and 59. The opposite ends of the leads 58 and 59 (respectively designated 63 and 64) extend outwardly through the associated ones of the slots 27 and 34 to provide external terminals for the coil 47.

The portions of the leads 58 and 59 extending over the core are rigidly supported on the underlying taped coil 47 by wrapping an additional layer 66 (FIG. 7) of insulating tape over the leads 58 and 59. The resultant bobbin-wound coil structure, designated generally at 67 in the figure, may be employed in any suitable manner; e.g., to provide selective excitation of a sealed mercury or dry reed switch (not shown) supportable within a central bore 68 of the bobbin 18.

It will be understood that the above-described method "of fabricating an inductive coil and the resultant bobbinmounted structure are merely illustrative of the principles of the invention. Many variations and modifications will now become obvious to those skilled in the art. For example, if the Wire forming the coil is heavy enough, separate leads may be dispensed with and the wire itself extended outwardly through the slots 27 and 34 to form external coil terminals. Also, if desired, additional coils may be wrapped about the bobbin 18 for use, e.g., in transformer applications, in which case a plurality of additional radial slots may be provided in the inner and outer discs of the flange 24 to guide the additional coil wires and leads into and out of the bobbin core. In such a situation, the use of the reservoir 40 to provide additional buffer lengths of wire for ultimately terminating such additional coils will be generally the same as that described above in connection with a single coil. These and many other variations may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. In a method of terminating a wire coil wound on the core of an elongated bobbin that is provided with a flange having a plurality of apertures, the steps of:

respectively passing first and second butter lengths of Wire from the input and output of the coil outwardly through one pair of the apertures to terminate at first and second wire ends;

respectively passing the first and second wire ends inwardly through another pair of the apertures to project the respective buffer lengths over the coil; positioning a pair of leads through separate ones of a pair of the apertures to project over the coil and to terminate adjacent the first and second wire ends; and

conductively bonding the first and second wire ends to the respective adjacent ends of the leads.

2. In a method of forming a coil on a dielectric bobbin having a core and a flange on one end of the core, the steps of:

winding several convolutions of wire on the periphery of the flange;

advancing the wire over the core;

winding a predetermined number of convolutions of wire over the core to form the coil;

unwinding the wire from the flange;

laying the unwound wire over the coil; and

securing one end of a lead to the end of the overlaid wire to form a terminal of the coil.

3. A method as defined in claim 2, further comprising the step of affixing the secure-d lead to the coil.

4. In a method of forming a coil on the core of an elongated bobbin that is terminated by a flange having a reservoir and a plurality of slots extending axially therethrough to interconnect the core and the reservoir, the steps of:

laying a first buffer length of wire in the reservoir, the

first buffer length commencing with an inner end of the wire;

passing the wire inwardly from the reservoir to the core through one of the slots;

winding a second length of the wire on the core to form the coil;

passing the wire outwardly from the core to the reservoir through another one of the slots;

laying a second buffer length of the wire in the reservoir to terminate at an outer end of the wire;

separately passing the wire in the first and second buffer lengths inwardly through a pair of the slots to project the inner and outer ends of the wire over the wound coil;

respectively laying first and second elongated leads in a pair of the slots to project over the coil and to terminate adjacent the inner and outer ends of the wire; and

conductively bonding the inner and outer ends of the wire to the adjacent ends of the leads.

5. A method of forming a coil on a dielectric bobbin wherein the bobbin has a core terminated by a flange that is provided with a first circumferential slot and a plurality of spaced second slots extending inwardly from the flange periphery, which comprises the steps of:

winding a first predetermined number of convolutions of the wire in the first slot in the flange;

feeding the wire inwardly through one of the second slots to the core;

winding a second predetermined number of convolutions of the wire on the periphery of the core to form the coil;

wrapping the coil with insulating material;

feeding the wire outwardly through another one of the second slots;

winding a second predetermined number of convolutions of wire in the first slot;

severing the wire;

unwinding the first and second convolutions of wire in the first slot;

separately feeding the unwound wire from the first and second convolutions inwardly through a pair of the second slots to overlie the wrapped coil;

attaching elongated terminals to the ends of the unwound wire to extend outwardly through a pair of the second slots; and

wrapping additional insulating material around the portions of the terminals overlying the wrapped coil.

6. A method of forming a coil on an elongated bobbin core, which comprises the steps of:

terminating one end of the bobbin core with a dielectric flange having a mounting boss, a peripheral edge, and a plurality of mutually spaced slots extending axially through the flange;

temporarily anchoring an input end of a wire to the boss;

winding a first length of the wire around the peripheral edge;

passing the wire inwardly through one of the slots to the core;

winding a second length of the wire around the core to form the coil;

passing the wire outwardly through a second one of the slots to the peripheral edge;

winding a third length of the wire around the peripheral edge;

temporarily anchoring the outer end of the third length of wire to the boss;

severing the wire;

unwinding the first and third lengths of the wire from the boss and the peripheral edge;

respectively passing the unwound first and third lengths of wire through a pair of the slots and over the coil to terminate at first and second wire ends;

soldering like ends of a pair of leads to the first and second wire ends; and

laying the opposite ends of the leads in a pair of the slots to project outwardly through the flange.

7. An inductive coil assembly, which comprises:

an elongated dielectric bobbin having a core and a flange terminating the core, the flange having a plurality of spaced apertures extending axially therethrough;

a first length of insulated Wire convolutely wound about the periphery of the core to form a coil;

a second length of insulated wire extending outwardly from one end of the coil through a first one of the apertures and inwardly through a second one of the apertures to project over the coil and terminate at a first wire end;

a third length of insulated wire extending outwardly from the other end of the coil through a third one of the apertures and inwardly through a fourth one of the apertures to project over the coil and terminate at a second coil end; and

a pair ofi elongated leads respectively extending inwardly through a pair of the apertures to project over the coil and to individually engage the first and second wire ends.

8. In a coil bobbin having an elongated core terminated by a flange, an improved flange construction which comprises:

an inner disc aflixed to the core and having a plurality of mutually spaced first apertures extending axially therethrough from the core;

a central disc axially abutting the inner disc, the central disc having a peripheral surface smaller in diameter than that of the inner disc and communicating with the core through the plurality of first apertures; and

an outer disc axially abutting the central disc, the outer disc having a peripheral surface larger in diameter than that of the central disc and a pair of mutually spaced second apertures extending axially through the outer disc in respective alignment with a pair of the first apertures in the inner disc.

References Cited UNITED STATES PATENTS 2,949,591 8/1960 Craige 336-208 X ELLIOT A. GOLDBERG, Primary Examiner U.S. Cl. X.R. 

